(CBSNews) OMAHA, Neb. -- The Nebraska State Patrol has for years forced female recruits to submit to invasive, medically unnecessary pelvic exams performed by a male doctor before they can be hired, according to a new federal lawsuit that has prompted a criminal investigation.

State Trooper Brienne Splittgerber filed the lawsuit Tuesday against the patrol, the state of Nebraska, two former patrol heads and various other people, accusing them of creating a hostile work environment for women.

"Immediately upon learning of these allegations in June, the Governor instructed his Chief Human Resources Officer to review this matter, which has subsequently resulted in a criminal investigation by the State Patrol," Taylor Gage, a spokesman for Gov. Pete Ricketts, said in a written statement Wednesday.

State Patrol spokesman Cody Thomas said no NSP recruits have undergone the pelvic exams since December 2016. Thomas did not comment on who was under investigation.

The lawsuit seeks unspecified damages, saying women recruits for years have been required to undress from the waist down for a vaginal and rectal examination. The lawsuit says Splittgerber was told the exam was required to check for hernias, but male recruits were generally not required to undress or undergo such invasive exams.

"Subjecting the plaintiff and other female trooper candidates to a medically unnecessary and sexually invasive procedure is outrageous conduct which goes beyond all possible bounds of decency and is utterly intolerable in a civilized community," according to the lawsuit, filed by Omaha attorney Tom White.

Splittgerber submitted to the exam in 2014 before she was hired by the patrol in 2015, saying in her lawsuit that she was required by a Lincoln doctor hired by the patrol to remove her pants and lie on her back, then her stomach, to be examined.

Splittgerber complained to her superiors after being told by her family doctor that there was no legitimate medical purpose for the exam. She was told an investigation was underway, the lawsuit says, but was disturbed that female patrol candidates from subsequent recruitment classes continued to be sent to the same doctor to submit to the exams.

Dr. Karen Carlson, an OB-GYN with Nebraska Medicine in Omaha, said it would be highly unusual to conduct a pelvic exam for a possible hernia. Pressing the abdomen with a hand would be standard for such a check, she said.

"There would be no reason to look in the genital or anal area," Carlson said. "We might have them loosen their pants, but I wouldn't think there would be any need to disrobe."

An attorney for the State Patrol declined to comment Wednesday, citing the pending litigation, and referred questions to the Nebraska Attorney General's office, which will defend the patrol and state against the lawsuit. A spokeswoman for the Attorney General's office would say only that her office is currently reviewing the lawsuit.

The lawsuit is the latest of several controversies that have hounded the patrol in recent years.

Earlier this year, Ricketts fired Col. Brad Rice, who was the head of the Nebraska State Patrol during most of Splittgerber's tenure with the patrol. His firing came amid an internal review launched after officers were accused of changing their story about a crash that killed a South Dakota driver who was fleeing from a trooper.

Rice's firing followed a union survey of state troopers that found widespread dissatisfaction among rank-and-file employees with the agency's management.

Ricketts appointed Rice as head of the agency in 2015 despite concerns that Rice was complicit in gender discrimination while he was a captain in the patrol. Rice served on an interview panel that denied several promotions to a female sergeant, who successfully sued for gender discrimination. Rice was also accused of saying that women shouldn't be in law enforcement - a comment Rice said was taken out of context.